Cerebrovascular system

15% of CO devoted to CNS

From the LV blood goes to:

1. Brachycephalic trunk

2. Left common carotid artery

3. Left subclavian artery

Blood to CNS goes via 2 systems:

1. Carotid (anterior) system - main source of blood supply ICA

2. Vertebral-basilar (posterior) system

The major arteries that enter the cranium from both system located at the subarachnoid space.

Both systems forms the circle of Willis

• Between the left and right ACA (at junction of A1-A2 segments) - ACoA

• Between the PCA and ICA (C7) on both sides - PCoA